The more organizations link together, the stronger the message. The whole is greater than the sum of the parts. Individual organizational maps linked together in a network create a stronger message than stand-alone websites. This is because the maps can be cross-linked, and thus the message about a topic (e.g. climate change) can come from multiple sources at the subject level (horizontal cross-linking) and the vertical (at the name level).
That is to say, it helps to overcome the "belief barrier," which boils down to mistrust of a single source.